ESR of an Mn2+-S2- complex center in KCl crystals

Electron spin resonance of MnS-doped KCl crystals has been investigated. It was found that as-grown samples show a simple spectrum looking like being constructed from eighteen resonance lines. The spectrum was very stable at room temperature and the same spectrum was also obtained after annealing of quenched samples which exibit only well-known spectra due to two types of Mn 2+ -vacancy complex centers. Such a spectrum characteristic of as-grown samples was analysed using a model of an Mn 2+ –S 2- complex center in an orthorhombic crystalline field basically with principal axes along cubic crystal axes, two of which are tilted by 10° from crystal axes. When as-grown samples were cooled down to about 150 K, the tilt angle decreased to zero and the crystalline field surrounding the center changed from orthorhombic to nearly tetragonal. It was also found that the Mn 2+ –S 2- complex center responsible for the 18-line spectra disappears by uv irradiation.